Optically-detected charge density dynamics in organic lightemitting diodes (OLEDs)

摘要

Electro-modulation (EM) is used to measure interfacial hole densities in operating OLEDs. This in-situ optical probe has provided us with a measure of relative hole and electron currents in a wide range of OLED structures. Insight to the dynamics of interfacial hole densities allows an assessment of the longterm stability of electron-hole balance, and therefore helps greatly with the identification of electroluminescence (EL) degradation mechanisms. Here, we limit the investigation to NPB/AlQ_3 OLEDs, but note that the technique is versatile, and can be readily adapted to a wide range OLED structures, especially those comprising arylamine -based hole transport materials and interlayers.